1. Field of Invention The present invention relates to a printed circuit board.
2. Description of Related Arts
The printed circuit board employs an insulating board as a base material, and is cut into a certain size. At least one patterned conductive layer is attached onto the board and holes are arranged thereon (for example, component holes, fastening holes, and plated-through holes). The board is used for replacing the base on which electronic devices are mounted, and for connecting the electronic elements. This type of board is made by means of electronic lithography, and is therefore referred to as a printed circuit board. The printed circuit board is an important electronic component, and supports electronic devices.
Electronic products are becoming smaller in size and have more functions, and the size of the printed circuit board is also becoming smaller. However, the number of via holes and the interference between signal lines have constantly restricted the size reduction of the printed circuit board; hence, it is difficult to make a breakthrough in substantial size reduction of the printed circuit board. For example, if the pad at the edge of the via hole is too close to the signal line arranged near the pad, interference will occur. So, a certain distance should be maintained between the via hole and the signal line. For another example, the via hole of the printed circuit board is closely related to the circuit connections of the electronic devices arranged on the printed circuit board and/or the circuit connections among multiple layers of printed circuit boards. Therefore, each circuit connection requires a via hole; as a result, the size and the number of via holes further restrict the size reduction of the printed circuit board.
Therefore, to improve the via hole so as to effectively reduce the size of the printed circuit board is a problem that needs to be solved by persons skilled in the art.